1. Field of the Invention
The present invention relates to hard disk drives (HDDs). More particularly, the present invention relates to a technique for increasing the format efficiency of an HDD.
2. Description of the Related Art
FIG. 1 shows an exemplary hard disk drive (HDD) 100 having a magnetic read/write head (or a recording slider) 101 that includes, for example, an offset head, that is positioned over a selected track on a magnetic disk 102 using a dual-stage servo system for writing data to and/or reading data from disk 102. Customer data and servo sample data are recorded in arrays of concentric data information tracks on the surface of disk 102. While HDD 100 shows only a single magnetic disk 102, HDDs typically have a plurality of stacked, commonly rotated, rigid magnetic disks.
The dual-stage servo system of HDD 100 includes an actuator 105, typically a voice-coil motor (VCM), for coarse positioning a read/write head suspension 106 and a secondary actuator, such as a microactuator or micropositioner, for fine positioning read/write head 101 over a selected track. As used herein, a microactuator (or a micropositioner) is a small actuator that is placed between a suspension and a slider and moves the slider relative to the suspension.
The ratio of the amount of storage space available on an HDD to the actual stored customer data is commonly referred to as the “format efficiency.” Techniques that have been used for increasing the format efficiency include decreasing the length of the servo samples, increasing the numbers of tracks-per-inch and the number of bits-per-inch and minimizing the write-to-read recovery times. Nevertheless, the format efficiency of HDDs has not declined significantly from generation to generation of HDDs and new techniques for increasing the format efficiency are being investigated. Techniques that increase the areal density, however, increase the numbers of servo samples, increase the amount of error correction codes, and increase coding flush.
As the numbers of tracks-per-inch increase beyond 100,000 tracks-per-inch and the read-to-write head spacing requirements increase, the hard disk areal space that has been previously ignored is now significant and worth exploiting. Improving the overall format efficiency of a 300 GB hard disk drive by, for example, 1% would yield 3 GB of available space for customer data.
Consequently, what is needed is a technique that increases the overall format efficiency of a hard disk drive.